It is known that there is a potential difference inside and outside of a cell in a normal plant and electromotive force is generated. It is possible to describe a mechanism which generates such electromotive force based on, for example, an electrophysiological model of an axial organ of a higher plant. In particular, various methods are suggested in which a state of a root of the plant (for example, water stress) is examined non-destructively utilizing electromotive force between the root and soil.
As a prior technique in which water stress in a plant is measured utilizing the method described above, for example, Patent Document 1 is known. In Patent Document 1, connecting a first nonpolarizable electrode to the plant, connecting a second nonpolarizable electrode to soil in which the plant is planted, providing a potentiometer between the two nonpolarizable electrodes, and being able to measure water stress which is received by the plant by measuring electromotive force between both nonpolarizable electrodes using the potentiometer.
As for such parallax correction, a technology which performs parallax correction by acquiring a positional relationship of an image of a subject appearing in each captured image of two cameras by block matching based on edges and feature amounts, and deforming the image based on this information is known (refer to Patent Document 1). In particular, in this technique, a stitching point that defines the degree of deformation of the image at the time of the parallax correction is changed for each frame so as to generate an appropriate combined image for each frame.
Meanwhile, as an index for meaningfully measuring water content contained in a plant, for example, it is desired to quantitatively and visually suggest a time-transition of water stress in a growing process to an observer (for example, a user such as a farmer). In farms cultivating the plant (for example, vegetables such as tomatoes), in order to improve the value of tomato (that is, the unit price), for example, it is conceivable to improve the sugar content of tomatoes. Here, the kind of irrigation to be performed and the timing of the irrigation for increasing the sugar content is mainly attributable to artificial arrangements such as farmer's past experience and intuition. The amount of the water stress applied to the tomato is required to accurately predict to some extent in grasping irrigation timing so as to improve a sugar content of the tomato.
In general, increasing a sugar content of a fruit such as a tomato leads to quality improvement, and thus the unit price rises. On the other hand, since it is not easy to cultivate fruit such as tomato, yield is decreased and thereby production volume is decreased. In other words, there is a trade-off relationship between high performance of fruits and the yield. In the future, it is expected to increase the productivity by improving the yield.
An object of the present disclosure is to estimate water content contained in the plant by using an external standard sample has the same chemical properties as water, quantitatively and visually suggest a time-transition of the water content to a user, and early teach the timing of irrigation to the plant with high accuracy.